Integrated circuits frequently include analog components that require a stable reference voltage for operation. These stable reference voltages are preferably generated such that a substantially constant reference voltage is provided as an output, regardless of any changes that occur in the integrated circuit, such as fluctuations in the input voltage, temperature fluctuations and changes in the loading conditions. Bandgap voltage reference circuits are a type of voltage regulator that can be used to generate stable output voltages under a variety of conditions. A bandgap reference circuit utilizes the inherent bandgap exhibited by semiconductor materials to regulate a supply voltage in providing a stable and accurate output reference voltage.
In a voltage regulator that generates a reference output voltage based on a supply voltage, the dropout voltage or headroom of the regulator is the minimum differential between the supply voltage and output voltage for which the regulator can maintain a stable output voltage. More headroom provides greater cushion to the voltage regulator in maintaining a stable output voltage. However, the greater the headroom that is implemented by a voltage regulator, the larger the required supply voltage, and thus the less suited a regulator is for low voltage applications. As such, low headroom (i.e., low dropout) regulators are preferred in low power applications that rely on efficient use of available battery power. For instance, in certain low power applications, such as battery-powered remote sensors used for data collection, devices may operate within power constraints that require a battery life of months or even years. In such applications, voltage regulators preferably operate using low voltages and using minimal headroom.